3.3.- Flux Balance Analysis of the reduced model
Parsimonious Flux Balance Analysis approach (p-FBA) was performed using
Optflux 3.4 Software (Rocha et al., 2010), a user-friendly computational
tool for metabolic engineering applications. p-FBA is a variant of flux
balance analysis that minimizes the total material flow to achieve an
objective, while maintaining the optimal growth (Lewis et al., 2010).
The graphical representation of the p-FBA was generated using Omix
Visualization Software (GmbH&Co.KG), as described in Droste et al.
(Droste et al., 2011), where only the most significant fluxes for this
study were represented.
As usual in FBA with genomic models, the system was under-determined and
there existed some degrees of freedom. To find the optimal state, p-FBA
uses the optimization of a certain objective function, in this case the
maximum value of ATP generation (EF0002). Cytoplasmic malic enzyme was
considered to be inactive and NADPH required for biosynthesis could only
be regenerated by pentose phosphate pathway, as this degree of freedom
can only be solved using more advanced fluxomic techniques (R00216 [0
0]) (Quek et al., 2010). Glutaminolysis was constrained to go in the
direction of oxoglutarate generation (R00243mitoc [0 10000])
(McKeehan, 1986). Specific consumption/production rates of experimental
metabolites measured were added to the model using the mean of the
duplicates ± standard deviation.